The present invention relates to welding torches and more particularly gas shielded tungsten-arc welding torches, commonly referred to in the trade as TIG torches. The designation TIG refers to tungsten inert gas. TIG welding is an arc welding process originally developed to weld corrosion resistant and difficult to weld metals, such as aluminum and magnesium. The necessary heat for gas tungsten-arc welding is produced by a highly concentrated arc maintained between a non-consumable tungsten electrode and the workpiece to be welded which permits pinpoint control of the heat resulting in a narrow heat affected zone. This is obviously advantageous when welding metals that possess high heat conductivity, such as aluminum and copper. The weld zone, the molten metals and the tungsten electrode are shielded from the atmosphere by a blanket of inert gas such as argon or helium which is fed through the electrode holder. This inert shielding gas surrounding the weld zone serves to blanket the weld and exclude the active properties in the surrounding air thereby preventing oxidation of the electrode, the weld puddle and the weld zone.
While TIG torches are highly versatile in that they are capable of welding all types of metals, their rigid configurations have made their use quite difficult in many work areas of limited or difficult access. As a result, different torches have been provided with different head configurations for use in such areas. For example, one torch with a given head configuration may emit the arc at an angle of about 70 degrees with respect to the handle, another at 90 degrees with respect to the handle, and yet another torch would emit an arc in axial alignment with the torch handle. To utilize this form of flexibility, however, is somewhat time consuming and it is necessary to maintain several different torches of varying head configurations which is very expensive. An attempted solution to this problem is found in U.S. Pat. No. 2,949,526, wherein a body portion of the torch was made removable from the torch handle. However, this approach did little to remedy the situation as the removable body not only comprised the head portion of the torch, but most of the remaining elements as well. Consequently, to maintain an inventory of TIG torch body portions with different head configurations is almost as costly as maintaining an inventory of torches.
Another attempt to increase the versatility of gas shielded welding torches is found in U.S. Pat. No. 4,145,595 wherein the torch body is constructed so as to be bendable so that the torch head can be positioned in any desired angular orientation with respect thereto to access the work area. To provide such flexibility, a double helix formed by a pair of side-by-side coils of flexible conductive wire each cylindrical in cross-section is provided between the torch handle and the torch head. The coils electrically and structurally connect the torch head with the torch handle while the interior central bore thereof defines a gas supply conduit to the torch head. A cylindrical body of an elastomeric insulating material is molded about the helix and adjacent coupling members such that the insulating material is interposed between and adhered to the convolutions of the helix. The patent states that by embedding the helix in the body of insulating material, the displacement of the metal coils is limited, minimizing the work hardening of the helix and prolonging its useful life. It has been found, however, that because the encapsulating of the helix in the insulating material is done by a molding operation that requires heat and pressure for the insulating material (usually silicone rubber), the insulating material is forced by the molding pressure into all of the available open areas within the component assembly. As a result, the insulating rubber is forced down between the convolutions of the helix and into the internal gas supply conduit formed by the bore of helix, reducing the ability of the coils to flex and plugging or partially plugging the internal gas conduit. Plugging of the conduit is avoided with the use of a removable rod which extends through the helix during the molding process to prevent the insulating material from entering the spaces between the convolutions of the helix. After the insulating material is cured, the rod is removed. Such a process requires relatively expensive tooling, increasing the costs of manufacture and exacerbates the flexibility problem resulting from filling the areas of the helix between the convulsions with insulating material.
With the rod in place to prevent entry of the insulating rubber into the bore of the helix, the insulating rubber is tightly packed between the convolutions of the helix and, by design, bonds thereto. The metal component surfaces of the assembly are treated by sand blasting or by similar cleaning action to achieve this bonding and maximize the adhesion of the rubber insulation thereto. As a result, not only are the individual coils in the helix prevented by the interposed rubber from freely opening and closing as intended to provide flexibility, the flexibility in the system is, in effect, provided almost solely by rubber material between the coils.
As the user bends the torch handle, the coils in the area of bending and the attached adjacent rubber form a radius of curvature. As these coils and surrounding insulation in the handle are bent, rubber insulating material between the coils at the outside of the formed radius of curvature is stretched while the material at the inside of the radius is compressed. The stretched and compressed rubber insulating material thus tends to straighten the helix making the desired torch head orientation more difficult to achieve. More significantly, the individual coils in the helix are not perfectly symmetrical and the spacing between the individual coils will vary. As the bending tends to occur at the point of least resistance, the assembly will tend to bend repetitively in the areas of the helix with the most rubber between the coils, creating localized stresses in the helix and causing the repetitively bent coils to work harden and prematurely fail. Further, as the rubber insulation is bonded to the coil, the repetitive bending at points of least resistance results in repetitive stretching the adjacent rubber insulating material which can lead to tearing of the rubber, further reducing the localized resistance to bending and increasing the likelihood of premature failing. Tears and splits in the insulation also can expose the electrically conductive metal helix which can cause arcing, sparks and electrical shock to the operator.
The torch of the present invention represents an improvement over that disclosed in U.S. Pat. No. 4,145,595 in that it retains the inherent flexibility of a helix coil uninhibited by the presence of the insulating material without sacrificing the structural integrity or operability of the torch and without the need for costly tooling. The present invention also provides a second layer of thermal and electrical insulation for the torch to protect the operator. As a result, the present invention provides a safer and more flexible torch at a lower cost with an increased useful life.